Deposition systems are used to deposit a substance on a substrate. Several types of conventional deposition systems are currently implemented. One type of conventional deposition system implements magnetron sputtering. Sputtering, in general, is the process of ejecting atoms from a solid target material, the target or cathode, to deposit a thin film on a substrate. A magnetron enhances this operation by generating strong electric and magnetic fields to trap electrons and improve the formation of ions from gaseous neutrals such as argon. The ions impact the target and cause target material to eject and deposit on the substrate. During operation, an electric current may flow from the sputtering cathode to anode assemblies within the deposition system.
While some sputtering deposition systems use a cathode with a fixed anode (i.e., in a fixed position relative to the cathode), other sputtering deposition systems implement an anode that moves relative to the cathode. It should be noted that, while there may be multiple components of the deposition system which act as anodes, there may be a primary anode based on its relative area and proximity to the cathode. Hence, references herein to the anode generally refer to this type of primary anode, unless indicated otherwise. As an example of a moving primary anode, some deposition systems use a moving pallet to hold the substrates, and this pallet also acts as the primary anode during operation. In this way, the primary anode moves relative to the cathode, because the cathode is stationery within the deposition chamber, as the wafer pallet acting as anode moves into and out of the deposition chamber. In this type of system, where the anode moves relative to the cathode, several problems can occur.
One problem occurs where the substrate and the pallet, which carries the substrate, act as the primary anode. This problem derives from the failure to provide a consistent anode within the deposition chamber which results in a damaged substrate and in unstable cathode operation. The inconsistency is apparent where the wafer pallet and substrates form the primary anode and where there is intermittent electrical contact between the wafer pallet and the substrate, usually through the edge of the substrate. In this scenario, the pallet is typically coupled to ground and an intermittent electrical current may flow from the substrate to the pallet in the form of an electrical arc, resulting in heat. This discharge can damage the substrate, damage a device on the substrate, melt a deposited layer, or create a metal alloy from multiple deposition layers on the substrate. Consequently, the original material does not function in the same manner as the altered material. As an example, the altered material cannot be chemically processed (i.e., it does not etch away) so that subsequent patterning techniques fail. This failure of the patterning techniques results in failure of the device as exemplified by electrical shorts within the device.